Treatment of hydrocarbon oils



Patented June 8, 1948 TREATMENT OF HYDROCARBON OILS Darwin M. McCormick, Springfield, Pa., assignor to The Atlantic Refining Company, Philadelphia, Pa., a corporation of Pennsylvania No Drawing. Application June 8, 1946, Serial No. 675,330

The present invention relates to the solvent refining of hydrocarbon oils, and particularly petroleum lubricating oil stocks.

More specifically, this invention is concerned with a nitrobenzene extraction process wherein there is provided a novel method for avoiding emulsification diificulties and increasing the' effective capacity of extraction units which employ nitrobenzene as the selective solvent.

The use of nitrobenzene in the selective solvent extraction of lubricating oils is Well known in the art, and has been described in the Ferris United States Patent No. 1,788,569, and elsewhere. The nitrobenzene extraction process is applicable to all types of viscous petroleum oils, either waxy or non-waxy, be they either distillates or residuums. The extraction may be carried out batchwise, or in multi-stage counter-current systems, or in continuous towers, usually at temperatures below 100 F., and preferably at temperatures between 40 F. and 70 F. The operation of all of these systems is Well known in the art, and further detailed description thereof is here unnecessary.

In all solvent extraction processes, there must be an intimate commingling or contacting between the extraction solvent and the oil undergoing extraction. In a nitrobenzene-lubricating oil extraction system, particularly where the oil is non-waxy, there is always a tendency for the formation of emulsions of rafiinate phase in the extract phase, the rafiinate phase being rich in paramnic hydrocarbons and containing a small amount of solvent, and the extract phase being rich in naphthenic hydrocarbons and containing a large quantity of solvent. In batch, and in m'ulti-stage batch countercurrent systems sufficient settling area and settling time must be provided to permit proper stratification of the phases. In countercurrent tower systems, the velocity of flow must be such as to permit adequate separation of the phases. Thus, in all extraction systems the throughput is, to a considerable degree, limited by emulsification tendencies, usually the tendency of the railinate phase to emulsify in the nitrobenzene extract phase. It is therefore an object of this invention to avoid emulsification, particularly during the phase separation step, and thereby substantially increase the capacity of the nitrobenzene extraction units. I

I have found that when a preferentially oilsoluble alkaline earth metal sulfonate is added to a nitrobenzene extraction system in concentrations within the range of 0.01% to 0.1% and preferably 0.025% to 0.05%, emulsification difiiculties in the extraction system may be substantially reduced and the throughput of the system may be greatly increased. It is preferred to add the alkaline earth metal sulfonate in the form 7 Claims. (Cl. 196-1435) of an oil concentrate, for example, a 10% solution of sulfonate in lubricating oil. The sulfonate may be introduced directly into the viscous hydrocarbon oil charged to the system for extraction, or it may be added to the nitrobenzene or nitrobenzene extract at any point in the system. In systems where emulsification troubles develop in a particular stage or at a particular point in a tower, the alkaline earth metal sulfonate may be introduced directly at that portion of the system, or into the oil or nitrobenzene entering at that portion of the system. The sulfonate, once introduced into the system is not recovered, but passes from the system in the raflinate phase and in the extract phase, the major portion of the sulfonate occurring in the latter phase. Since the quantities of sulfonate used are so small, they have no appreciable efiectupon the properties of the raflin-ate or extract oils, and may be disregarded.

The alkaline metal sulfonates, such as the normal or basic sulfonates of calcium, barium, and strontium, may be produced by conventional methods from oil-soluble sulfonic acids. Such: sulfonic acids may be prepared by sulfonating hydrocarbon oils, particularly naphthenic oils, with concentrated sulfuric acid, 98% sulfuric acid, fuming sulfuric acid, sulfur trioxide, orchlorsulfuric acid. The resulting sulfonated oils, after removal of acid sludge, may be neutralized. with the appropriate base, e. g., calcium hydroxide or lime, barium hydroxide, strontium hydroxide, or the carbonates of these metals. Alternatively, the sulfonated oils may be neutralized with sodium or potassium hydroxide, and the resulting soaps may be extracted from the neutralized oil by treatment with a solvent such as ethyl alcohol-water or isopropyl alcohol-water, and the soaps so recovered then converted into the alkaline earth metal sulfonates by conventional methods. A preferred method of manufacture of the sulfonates is disclosed and claimed in United States Patent No. 2,361,476 to Higbee et al., and involves the direct neutralization of sulfonated hydrocarbon oil with dry lime, followed by filtration and concentration of the calcium sulfonate by distillation under reduced pressure.

In practicing the present invention it is unnecessary to modify any of the solvent extraction systems or treating conditions, except to provide for the introduction of the alkaline earth metal sulfonate at the proper point and in the desired amount. While the addition of small amounts of alkaline earth metal sulfonate prevents emulsification difficulties and increases the capacity of a nitrobenzene extraction system, it has been found that alkali metal sulfonates such as the oil-soluble sodium and potassium sulfonates, do not inhibit emulsification, but in fact aggravate ever, are not to be construed as limiting the scopethereof.

A commercial S-stage batch countercurrent nitrobenzene solvent extraction system wasop erated at 40 F. using a relatively non waxy lubricating oil stock and nitrobenzeneat'a-charge ratio of 1 to 1 by volume. The charge-oil-hadfa the alkaline earth metal salts of oil-soluble petroleum sulfonicacids are-preferred, the corresponding oil-soluble salts of other sulfonic acids may be used, including the alkaline earth metal salts of sulfonated fatty oils, sulfonated phenols particularly th'ose. containing long chain alkyl groups, alkylpolyethoxy sulfonates, alkyl phenyl polyethoxy sulfonates, and sulfonated aromatic hydrocarbons'containing long chain alkyl groups.

S. U. viscosity of 198 seconds at 100 F., an A; P.'I:. gravity of 25.5", a pour point of R, an, H

A. S. T. M. color of 2 /2D, a viscosityindex of 72, and a viscosity-gravity constant of 0.848. When no alkaline-earth'metal sulfonate was added} considerable diffi' cultywas encounteredin obt'a'ining rapid and efficient stratification-of the raffirlate and extract phases in-the settlers, due tommulsifibation of the finely divided raiiinate droplets in th'e extract phase. The slow settling rate,-with the resultant poorly defined interface between the phases, caused contamination of the raffinat'e phase with theext'ract', and vice versag-with simultaneous degradation of product quality and lower" product yield. Furthermore, this diiiiculty encountered in the settlers caused overloadingot the evaporators for the recovery of nitrobenzene from the oil fractions and'necessitated operation at reduced charge rates. However, whensmall amounts ofalkaline earth metal sulfonate' were added to'the charge oil, emulsification was greatly reducedand stratification and settling rate was substantially increased, with resultant increase in: product quality and yield.

The specific'sulfonate employed was obtained by treating a naphthenic lubricating oil fraction with 4 dumps of'5% by volume'each of 98% sulfuric acid at 160F.-180 F., removing-the acid sludge, neutralizing the sulfonated oil with lime, brightening the neutralized oil by air blowing, filtering of excess lime and insoluble salts, and distilling the neutralized oil under reduced pressuret'o give a concentrate of about 30% of calcium sulfonate-in the oil. This concentrate was diluted'w-ith lubricating oil stock to give a sulfonate concentration of about 10%, and this product was added in small amounts to the charge oil entering the extraction system.

The results obtained with and without the addition-of the sulfonate are given in the following table:

Oil'Stock Charge, ,bbls. per day- Calcium Sulfonote added Settler surging Rafilnote Yield, Vol. Per cent S. U. Yis; at 100 F A. P. I. gravity Viscosity Index Viscosity-Gram Constant... A. S. T M. Color Pour-Point, F

Extract Yield, Vol. Per ce S. U. Viscosity at 100 F..- A; P. I. Gravity 19 Viscosity Index Viscosity-Gray. Constant A. S. T. M. Color PourPoint', F .l

1875 None Considera- While in Examples 2 and 3, an oil-soluble calcium sulfonate was employed to assist settling and separation-of the phases, similar results may be obtained using the normal or basic oil-soluble sulfonates of barium: and strontium, Although In most oases-itis unnecessary to add more than about.0.05% of the sulfonate, although amounts upl-to.-0'.1% may occasionally be required. Quantities in excess of about 0. do not give a proportlonate-increase in effectiveness, and it is uneconomical but not detrimental to use such larger amounts.

The-present inventionis particularly adapted in the nitrobenzene extraction of'non-waxy hydrocarbon oils using amounts of solventofithe order of Va to 3 volumes per volume of charge oil. Waxy oils. usually are more amenable to settling, consequently there is less occasion. for the use of the alkalineearth metal sulfonates in the nitrobenzene extraction of these stocks, although even in this case the sulfonat'es may have a beneficial action in the settling of? the rafiinateand extract phases.

I claim:

1. The method of avoiding emulsification dlf ficultiesand promoting the separation of the. rat finatephase from the extract phase inthe selective solvent extraction of viscous hydrocarbon oil employing nitrobenzeneas the extraction solvent, whichicomprises'adding to the extractionsystem a small" amount of an oil-soluble alkaline earth metal sulfonat'e sufficient to promote phase separation.

2; The'method'of avoiding emulsification diificulties and promoting the separation of the railinate phase from the extract phase in the selective solvent extraction of viscous hydrocarbon-oil employing nitrobenezene as the extraction solvent, which comprises adding to the extraction system from 0.01% to 0.1% of an oil-soluble alkaline earth metal sulfonate.

31 The method of avoiding emulsification-difiiculties andpromoting the separation of the rainnate phase from the extract phase in-the selective solvent extraction of viscous hydrocarbon oil employing nitrobenzene as the extraction solvent,

which comprises adding to the extraction system from 0'.025'% to 0.05% of an oil-soluble alkaline earth metal sulfonate.

4. The method of avoiding emulsification difficulties and promoting the separation of the raffin'ate phase from the extract phase in the selective solvent extraction of viscous hydrocarbon oil employing nitrobenzeneas the extraction solvent, which comprises adding to the extraction system from 0101% to0.1% of oil-soluble calcium sulfonate.

5. The method of avoiding emulsification difilculties and promoting the separation of the raffinatephase from the extract phase in the selective solvent extraction of viscous hydrocarbon oil employing nitrobenzene as the extraction solvent, which comprises adding to the extractionsystem from 0.01% to 011% ofoil soluble barium sulfonate;

6; The method of avoiding emulsification difficulties and promoting the separation of the raffinate phase from the extract phase in the selective solvent extraction of viscous hydrocarbon oil employing nitrobenzene as the extraction solvent, which comprises adding to the extraction system from 0.01% to 0.1% of oil-soluble strontium sulfonate.

7. In the extraction of lubricating oil stock with nitrobenzene at a temperature between 40 F. and 70 F. to separate the oil into a raffinate phase rich in paraffinic hydrocarbons and an extract phase rich in naphthenic hydrocarbons, the character of the oil being such that substantial emulsification occurs during extraction, the method of accelerating separation of the phases which comprises incorporating in the oil a small amount of an oilsoluble alkaline earth metal sulfonate and effecting separation of the phases in the presence of said sulfonate at the aforesaid temperature DARWIN M. MCCORNIICK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 10 Number Name Date 2,383,768 Buis et a1 Aug. 28, 1945 2,411,105 Nixon et a1 Nov. 12, 1946 

